The present invention relates to information processing systems and more specifically to a system and method for allocating an execution interval to one of a plurality of logical processors of an information processing system for executing instructions by a physical processor of the information processing system.
In some modern computing systems, particularly multi-processor information processing systems, many more logical processors can be defined than there are actual physical processors. Logically partitioned computing systems typically adhere to this model, such that each logical partition (“LPAR”) of the computing system typically is assigned a limited number of physical processors, but a larger number of logical processors can be invoked for execution within the LPAR. In such case, each logical processor typically does not run all the time. Instead, each logical processor runs when it is invoked for execution by a super-privileged process on the computing system such as an operating system, referred to as a “host program.” Alternatively, a logical processor can be invoked by an entity which has even higher privileges, e.g., a supervisory control program such as a “hypervisor” which allocates resources among the logical partitions of the computing system.
Certain resources within each LPAR of the computing system are subject to being shared by the logical processors of the LPAR. For example, certain data structures in kernel memory, communication channel resources and address spaces may be shared by different logical processors which perform related tasks. However, in order to avoid contention for resources and avoid the possibility that shared resources will appear different to two different logical processors, each shared resource can be protected by a “lock” mechanism. When one logical processor has control over a particular resource, a super-privileged process stores data indicating that that resource is currently “locked,” such that it is not available for use by any other logical processor.
In view of the foregoing, the present application relates to an efficient way of handling when a particular resource is locked by one logical processor while another logical processor is seeking to use that same resource.